At Gen 5:1-6 onwards, why does the family tree of Adam appear to ignore Cain and Abel? It seems to start at Seth.
The fourth chapter of Genesis gives a partial linage of Cain after he killed Abel. But the linage of descendants from Seth is complete because the purpose of the genealogy is not to trace the ancestry of every person, but only the family line that began with Seth and ran up to Noah. While the linage listed in the 5th chapter of Genesis stops at Noah, the 3rd chapter of Luke details the complete genealogy from Jesus back to Seth, son of Adam, Adam, son of God.